Clear terpolymers



April 1, 1958 R. .1. sLocoMBE ETAL. 2,829,125

v CLEAR TERPOLYMERS Filed D60. 7, 1953 3 Sheets-Sheet l v 5r/@nua A A AVAVAVAVAVA V V V V V AAAAA.

AAMMMM AMA/WMM IN VEN TOR`S April 1,1958 R. J. sLocoMBE ET AL 2,829,125

CLEAR TERPOLYMERS Filed Dec. 7, 1953 3 Sheets-Sheet 5 vAvA AvAvAvAv/ vv AAA/vw AAAAVAA A Wmvga/Qm .Avynvmwgvu Aww /WWMAA/vx/wAy/W VWANWMMAMANMVW INVENTOR.

'United States Patent() *This finvention relates to three-component interpolyjmei's, commonly called terpolymers, i. e., interpolym'ers lprepared by polymerizing a monomeric mixture consistjingV of three ditterent monomers. In yspecific aspects the "invention pertains to terpolymers of (a) a monomer Lselected from the group consisting ofl styrene, vinyltoluene, and vinylxylene, (b) methyl vinyl ketone, and (c) yamonomer selected from the group consistingfof acrylic acid, methacrylic acid, methacrylonitrile, alkyl "methacrylate, monoalkyl fumarate, and monoavlkyl vmaleatei Other aspects of the invention relate to improved :methods of preparing clear terpolymers.

It vis "by 'now well known that ethylenically unsaturated monomers differ greatly in their polymerization reac- A'tvity'toward each other. There are'in fact'some monomers that will not undergohomopolymerization at'all, i. e., polymerization of two yor more molecules 'offthe same monomer to form a polymer of that monomeryyct will Areadily undergo interpolymerization with certain other monomers. interpolymerization affords a method offimparting `varying characteristics to a polymer,f'faiid 'in many instances such characteristics cannot be obtained by mere physical admixture of two or` more homopolymers.v However, because of the above-,mentioned differ- .,e'ncjes in reactivity among monomers toward each other,

marked heterogeneity is the rule in interpolymersy 'and 'only under special circumstancesca'n an interpolyner 'jbe obtained that is of suflicient homogeneity togive-"fa transparent or clear interpolymer. While'soine objectionable properties such'as color, encountered ininter- `polymers, can often be "avoided by means suchas the use of'stabilizers or lower polymerization temperatures, ,incompatibility manifested by haze, turbidity,y or opacity in plasticsis not overcome by such treatment.

` L'If a monomeric mixture is subjected to polymerization `and the initial increment of polymer is segregated before the polymerization is allowed to go forward `to an lappreciable extent, it is frequently possible to obtain aclear interpOIymer, but the commercial impracticability of such vstages of polymerization is decient in the more'reactive monomer. There results a polymeric material which is 'jmade up of a variety of polymer molecules running a gamut'of compositions such that the total polymer is heterogeneous with resultant opacity and `often 'greatly impaired physical properties. This phenomenon, resulting in an undesirable product, can be overcome to an appreciable but limited extent by gradually adding during vtliefcourse of the polymerization the more reactive mono- ',mefat `a rate aimed at keeping the compositionof iin- "forward sutiiciently to permit a certainf'amount `ofpre- "dictabilityin vthis eld. It has been theorized that 'in'a "simple binary system involving the free-radical-init'iatd polymerization o'f onlyv two monomers, thecomposition fof polymer will be dependent only upon the ratel of four "mer molecules.

v n 2,829,125 Patented Apr. l, 1,958

ICC

reacted monomeric mixture essentially constant. As a practical' matter it-is extremely difficult to approach uniformity invsuch an operation, and itis impossible to Vvuse this techniqueat all in the case of mass (bulk.) polymeriz'ation in which the polymerization reaction 4mixture sets up into'semi-solid'or solid polymer lafter the reaction is only partly completed so that furtherl access of added monomer to the total mixture cannot'be, obtained.

' It is only in recent years that systematic laboratory and theoretical studies of interpolymerza'tion have gorie propagation steps, i.l e., steps in the propagation ofpoly- Thus, taking a systemlinvolving two monomers, M1 and M2, a growing polymerl chainfca'n have only'two kinds of active terminal groups, Vi. e., ja group derived from M1 ora group derived from M3. Either'of these groups hasA the possibility of'reacting -with either Mlor with M2. Using my and m2; to indicate these active terminal groups, the fourv possible reactions are as follows:

"initial copolymer formed from agiven mixture of :the 'monomers as follows:

about@ iMLHtMa Theiterms r1 and r2 are called reactivity ratios..,=A

very considerable body of experimental work hasy ingeneral confirmed the copolymer composition equation. A large proportion of possible pairs of monomers-are incapable, because of their-respective reactivity ratios,

ofl forming under any conditions aninstantaneousfpolymer having the `same compositionas .the ,monomeric mixture from which it is formed. Howevernthere are certain monomer pairs which, in a proportion characteristic of that pair, give a rcopolymer having the same composition as the particular monomeric mixture. ;In lauch instances, a batch polymerization canlbe carried out with amonomeric mixture of the particular composition with a, resultant homogeneous copolymer containingy thesame relative'proportions of the monomers asintheinitial monomeric reaction mixture. .This Vcomposition isknown as -.the polymerization `azeotrope composition, .and is representedby the equation: [Md TLl i s ,IMJM Su-chan azeotrope 'composition canvexist vt'ztrilyfforthose monomer pairs `wherein both r1 and r2 are lessV than V, for, theoreticallyvwherein both r1 a'n'drg are"g1'jeate r than vonefalthough no examples of thelatter combination'i'e known.

While an understanding of interpolyrnerization involving only two monomers is now possible to a considerable extent, because of the development of the above-discussed theories, an increase in the number of monomers to three or more obviously tremendously increases the possibilities and complications. Thus, for exampletif interpolymers of 100 monomers are to be considered, there are about 5000 possible monomer pairs, but about 160,-

000 different combinations of three monomers are possible, and for each of these 160,000 combinations the variations in `relative proportions of the three monomers are innite. If` the assumptions made in the development of the copolymer `composition equation still hold true where three monomers are to be interpolymerized, it is apparent that the composition` of the terpolymers formed at any givenlinstance will now be dependent upon the rate of nine propagation steps which are dependent upon the relative concentrations ofthe monomers in the monomeric mixturcand the reactivity ratio between each of the pairs of the monomers in the mixture. It has been -pointed out that the study of terpolymers can be sim- .plified` somewhat by application of the copolymer compositionequation, suitably modified for three-component systems, so as to eliminate from consideration monomers whose ability to interpolymerize is so slight that further `investigation of such combinations is obviously not war- `very desirable property of clarity. These terpolymers are made by polymerizing a monomeric mixture of certain proportions of three monomers. The proportions giving clear terpolymers will varyi from yone monomeric mixture to another depending upont the particular monomers present` inthat mixture. The invention is particularly `appliedto monomeric mixtures consisting essentially of (a) a monomer selected from the group consisting of styrene, vinyltoluene, and vinylxylene, (b) methyl vinyl ketone, and (c) a monomer selected from the group consisting of acrylic acid, methacrylic acid, methacrylonitrile, 'alkyl methacrylate, `monoalkyl fumarate. monoalkyl ma- `lente. For example, a -monomeric mixture consisting of styrene, methyl vinyl ketone, and acrylic acid will, when subjected to free-ra'dical-initiated batch polymerization, *give aclear ternolymer only if the relative proportionsot'` styrene, methyl `vinyl ketone and acrylic acid are properly chosen in a` manner to be hereinafterde scribed. ln contrast, a monomeric mixture consisting of styrene, methyl vinyl ketone, and `methyl methacrylate will give a clear terpolymer on being subjected to freeradical-intiated batch polymerization only if the relative proportions `of the three mentioned monomers in the monomeric mixture are within certain limits `which in general are different from those of `the aforementioned mixtures of styrene, methyl vinyl ketone and acrylic acid and yet which are chosen in accordance with the `-same principle now to be discussed.

` We-have found that clear terpolymers of the fnature described are made provided the proportions of three monomers in the monomeric mixture are chosen from the area lying along the line joining the binary polymerization azeotrope composition of the particular (a) and methyl` vinyl` ketone on the one hand,` and the binary polymerization azeotrope composition of the particular and the particular (c) on the other hand, as plotted on a triangular coordinate graph. By way of example, taking the case where (a) is styrene and (c) is acrylic `range from hazy to opaque materials.

acid, the point of the binary azeotrope composition of styrene and methyl vinyl ketone is placed along one side of a triangular coordinate graph at the proper location between the apex designating percent styrene and the apex designating 100 percent methyl vinyl ketone. This point is 57.7 weight percent styrene and 42.3 weight percent methyl vinyl ketone. On the opposite side of the equilateral triangle, constituting the triangular coordi nate graph, is placed the point representing the binary azeotrope composition of styrene and acrylic acid, this, of course, being located at the proper position on the side of the triangle between the apex representing 100 percent styrene and the apex representing 100 percent acrylic acid. This point is 56.1 weight percent styrene and 43.9 weight percent acrylic acid. Now a straight line is drawn between these two points. This line cuts across the triangular coordinate graph, without touching the side of the triangle opposite the styrene apex, which side represents varying proportions of methyl vinyl ketone and acrylic acid in binary mixtures of same. Methyl vinyl ketone and acrylic acid do not form a binary azeotrope. The said straight line joining the twopoints of binary azeotrope compositions describes three-component monomeric mixtures which, when subjected to freeradical-initiated batch polymerization, give clear terpolymers. Further, there is an appreciable area lying on each side of said line in which the terpolymers are essentially clear. However, one cannot go too far from this line without producing terpolymers which are not clear but The invention particularly applies to the area lying within 5 percent on each side of said line; said 5 percent is measured on the graph in a direction normal to the line, and is equal to live one-hundredths of the shortest distance between an apex and the side of the triangle opposite the apex. Terpolymers made by polymerizing a monomeric mixture having a composition lying in the area within 5 percent on each side of the line joining the two binary polymerization azeotrope compositions, are generally clearer than polymers made from similar monomeric mixtures lying farther away from and on the same side of the line. In

most systems all terpolymers made from monomeric` mixtures having compositions in the area lying within 5 percent on each side of the line are clear. In some systems the area of clarity may not extend as far as 5 per cent from the line. Those skilled in the art, having had the benet of the present disclosure, can easily determine by simple tests of the nature described herein which monomeric mixtures give clear terpolymers in a given polymerization system. In all events, the compositions of monomeric mixtures giving clear terpolymers will be found to constitute an area lying along the line joining the two binary polymerization azeotrope compositions.

The reasons for the clarity of terpolymers made as described are not known. The line joining the two binary azeotrope compositions does not represent what might be called aseries of three-component azcotropes. From much detailed data which we have obtained, the relative proportions of the three monomers in terpolymers made from monomeric mixtures lying along said line are not identical to the monomeric mixture from which the terpolymer is being prepared. In other words, during the course of a batch polymerization of a monomeric mixture whose composition is taken from the line, the composition of residual monomeric material drifts and the terpolymers so formed are not homogeneous mixtures of polymer molecules all of which contain monomer units in the Same ratio, but rather are mixtures of polymer molecules having varying proportions of the three monomer units therein. No heretofore known scientific facts or theories of interpolymerization explain our discovery. However, regardless of the various reasons for believing that terpolymers made from compositions lying along the line as aforesaid would be heterogeneous, and regard less of the actual reasons for the clarity of such terpolymers, it is apparent that the present invention makes possib1`e"'th'e` production of clear `terpolymerswith 'obvious attendant advantages, especially in films and molded articles made from the 'terp'olymers The accompanying drawings are triangular coordinate graphs showing compositions of some three-component monomeric mixtures that give clear terpolymers on being subjected to free-radical-initiated batch polymerization.

Figure I represents the system styrene/methyl vinyl ketone/acrylic acid. u v

Figure II represents the system vinyltoluene/methyl vinyl ketone/methacrylonitrile.

Figure III represents the system styrene/methyl vinyl ketone/methyl methacrylate.

By the present invention we can subject a given monomeric mixture consisting of three monomers, selected as described herein, to a batch polymerization and carry the polymerization reaction to complete .or essentially complete, say 90 to 100 percent, conversion of all of the monomers and yet obtain a clear solid resinous terpolymer. I-f desired, the polymerizationl can be stopped'at any point short of completion so long as polymeriza-f tion conditions are such as toproduce' solid terpolymer, but this is not necessary in order to obtain a clear terpolymer and would seldom be advantageous. The higher the degree of conversion of monomeric mixtures, the greater the advantages of our invention. This is because the greatest extent of heterogeneity is found with complete conversion to polymers. A high conversion, i. e., at last 50 weight percent conversion and preferably at least 8 0 weight percent conversion, is preferred in 'practicing the invention. However, some of the benefits of the invention may be realized even where the percentage conversion is as low as percent. With very low conve'rsions,`the polymer formed tends to approach the perfect homogeneity existing in the r'st infinitely small increment of polymer formed.l As pointed out above,'commer-cial practicality requires thatl conversion be carried to `a value more than a few percent, hence introducing the lack of homogeneity which up to now, the art has'not known how to avoid other than by techniques such as gradual monomer addition. It is to -be recognized that the extent of the area of clear terpolymers, lying along the line joining the two binary polymerization azeotrope compositions, is dependent not only on the particular polymerization system Ibut also on the percentage conversion," said area being being the greater the lower the percentage conversion, and the smaller the higher the percentage conversion. It is observed that the yterpolymers become clearer as the composition of the monomeric mixture approaches the line joining the two binary azeotrope compositions, the general rule being that clear est terpolymers are those derived from monomeric compositions 'lying on'the line.

It is usually desirable that the three-component monomeric mixture contain at least 2 weight percent, and preferably at least 5 weight percent, of the monomer present in thesmallest amount.

The invention is broadly applicable to any free-radicalinitiated interpolymerization of three-component monomeric mixtures containing the monomer combinations and in the proportions set forth herein, provided the polymerization is carried out by a batch procedure. By this it is meant that all of the monomeric materials to be employed are introduced simultaneously in the'desired proportions into the polymerization reaction system. Ordinarily a single charge of monomeric materials will be placed in a reaction vessel and the single charge subjected to polymerization conditions until the polymerization is substantially complete. However, it is not outside the scope of our invention to introduce continuously a monomeric mixture containing the three monomers in fixed proportions into a flow-type polymerization system, whereby the initial polymerizable mixture passes away from. its vpoint of introduction and ultimately is yrecovered erate temperatures of say on down to ',Of "CL process, and that additionally solvents, aqueous'reac as polymer. This c an be -accomplished by ,continuous ytiowingmofthe'monomeric mixture `into Athewriifstof a "cries of polymerization reaction vessels with continuous: flow of reaction mixture from one vessel to another al 1i a series of two or more such vessels withy ultimate 'ref covery of polymer from the last in the series. skilled yin. the art will understand that this operation is essentially a batch operation in the sense that additional monomeric material of composition different from the original mixture is not introduced into a partially poly-kA merized material. Thus, the term batch polymerization, as used herein, means a polymerization which does not involve the gradual or incremental or subsequ At addition o-f a monomer or monomers having a comp tion different from the initial monomeric mixture.l

The invention is perhaps most advantageously'effectedby the massy or bulk polymerization procedure. l`In siichf procedure the reaction mixture is free from adde'dsol" vent or other reaction medium'and consists solely i'o`f monomers, resultant polymers, and catalyst and regulator, if any. An important advantage ofthe invention is that such a mass poiyrnerization can be effected to pro-1 duce a clear terpolymer in a situation in which it is impossible to use the gradual monomer addition technique discussed above. It desired, the interpolymers of the present invention can be made by the suspension or the emulsion polymer-y ization techniques. For suspension polymerization a" action medium such as Water is used togetherwith Ya. small amount of suspending agent, for example tric'al-M cium phosphate, carboxymethylcellulcse, etc., -tog'ive Ya suspension of particles of initial monomeric mix which particles are not of such small size as to resul g a permanently/'stable latex. Wheretheparticlesare'ofi` quite large size, this type of polymerization is 'of called pearl polymerization. To effect emulsion poly# merization, suicient amount vof emulsifyingy agent, forex? ample a water-soluble salt of a sulfonated long chainalkylaromatic compound, a surface active condensation product of ethylene oxide withlong chain aliphatic alco-l hols or mercaptans, etc., is employed along 'with'vigorous agitation whereby an emulsion of the reactantsin 'water4 is formed and the product is obtained in the'forrnof 'a latex. The latex can then be coagulated if desired known methods and the polymer separated from the wa# ter. For some applications the latex can be employed cli-` rectly asfor examplefor forming a lilinjandfthe' res ingl film after evaporation of the water will be clear the polymers are made in accordance with the present vention. The emulsion technique Vhas certainadvanta particularly inthat a veryfhigh degree conversion4v of y monomers is obtained with considerable.rapidity,"sincet x e heat of reaction is easily carriedo by 'indirect heatfxchange with the reaction mixture which contains a t siderable proportion of water." Such polymerizations are often'eiected with redox-type catalyst systems at below. f The polymers of the present invention can alsobelnade in the presence of an added organic solvent. It shiild be recognized however that the presence of sucha.solvent'ordinarily results in a polymer of lower rri'oleculary weight than that obtained in the absence of the solvent;

Conventional recipes and procedures for effecting.

mass, solvent, suspension and emulsion polymerizafions v are so well-known to those skilled inthe art,"that','they need not be further detailed here. i From vthe foregoing, it will be apparent that the term, monomeric mixture, as used inthe claimsrefers to the polymerizable monomeric materials used 'in media, catalysts, etc., can be present or not inthe realc-l tion mixture as may be desired in any particularcase. In other words, in the claims monomeric mixture" is n.-v

assauts Polymerization can be effected by any of the wellklnown free `radical mechanisms. The polymerization is examples set forth hereinafter describe thermal poly-k merization in which the polymerization reaction was initited and maintained merely by heating the monomeric mixture in the absence of any added catalyst. In many instances it will be desired to add a suitable polymerizatin catalyst, in which case sufficient catalyst is employed to give a desiredreaction rate. Suitable catalysts are of the free-radical-promoting type, principal among which are peroxide-type polymerizationcatalysts, and azo-type polymerization catalysts. Those skilled in the art are now fully familiar with a large number of peroxide-type polymerization catalysts and a suitable one can readily be chosen by simple trial. Such catalysts can be inorganic or organic, the latter having the general formula: ROOR, wherein R is an organic radial and R" is an organic radical or hydrogen. These compounds are broadly termed peroxides, and in a more specificsense are hydroperoxides when R" is hydrogen. R and R" can be hydrocarbon radicals or organic radicals substituted with a great variety of substituents. By way of example, suitable peroxide-type catalysts include benzoyl peroxide, ditertiary butyl peroxide, tertiary butyl hydroperoxide, diacetyl peroxide, diethyl peroxycarbonate, 2- phenyl propane-Z-hydroperoxide, (known also as cumene hydroperoxide) among the organic peroxides; hydrogen peroxide, potassium persulfate, perborates and other per compounds among the `inorganic peroxides. The azotype polymerization catalysts are also well-known to those skilled in the art. These are characterized by the presence in the molecule of the group N=N bonded to one or two organic radicals, preferably at least one of the `bonds being to a tertiary carbon atom. By way ofY example 30E suitable azo-type catalysts can be mentioned ,a' azodiisobutyronitrile, p bromobenzenediazonium tiuoborate, N-nitroso-pbromoacetanilide, azomethane, phenyldiazonium halides, diazoaminobenzene, p-bromobenzenediazonium hydroxide, p-tolyldiazoaminobenzenc. The peroxytype or azo-type polymerization catalyst is used in small but catalytic amounts, which are generally not in excess of one percent by weight based upon the monomeric material. A suitable quantity is often in the rangeof. 0.05 to 0.5 percent by weight.

' Photopolymerization is another suitable procedure forcarrying out the present invention. This is ordinarily accomplished by irradiating the reaction mixture with ultraviolet light. Any suitable source of light is employed having effective amounts of light with wave lengths of 2,000 to 4,000 Angstrom units. The vessel in which the polymerization is conducted should be transparent to light of the`desired wave length so that the lightcan pass through the sides of the container. Suitable glasses are available commercially and include borosilicate (Py rex"), Vycor, and soft glass. Alternatively, the source of light can be placed `directly over the surface of the monomer in a container or can be placed within the reaction mixture itself. In some instances it is helpful to adda material that can be termed a photosensitizer, i. e., a` material which increases the rate of photopolymerization, for example organic disuldes as described in U. S. Patent No. 2,460,105.

Choice of a suitable temperature for a given polymerizationwll readily be made by those skilled in the art having beengiven the benefit of the present disclosure. In general, suitable temperatures will be found within the range of "`C.' to 200 C., although temperatures outside this range are not beyond the scope of the invention in its broadest aspects. The time required for complete polymerization will depend not only upon the temperature but also upon the catalyst if any is employed, the ability of the system to remove heat of polymerization, and the particular monomers employed. The examples set forth hereinafter give some illustrative information as to reaction times for particular polymerizations.

The term triangular coordinate graph as used herein is well understood. The accompanying figures are ex amples of such graphs and the use of same. However, for the sake of completeness the following statement can be made concerning the character of such triangular graphs. The graph is an equilateral triangle, divided off by three series of parallel lines each series being parallel to one side of the triangle. The distance between an apex of the triangle and the side opposite that apex represents variations in percentages of the component designated by that apex varying from percent to 0 percent in equal increments running from the apex to the opposite side of the triangle. tween the apex and the side of the triangle opposite the apex is divided into l0() equal parts by lines passing across the triangle and parallel to said side, each line represents l percent of the component for which that apex is designated. Thus, any point within the triangle represents a single threecomponent composition, the indicated percentages of the three components totaling 100 percent.

As an aid in the choice of suitable proportions of monomers for polymerization in accordance with the invention the following data on reactivity ratios of certain monomer pairs are presented by way of example. The values given are considered the best ones represented in the literature or otherwise known, (see Copolymers, by Alfrey,`Bohrer and Mark, lnterscience Publishers, Inc., 1952, pp. 32-43). In many instances an attempt is made to set forth an approximate order of accuracy. These latter figures, expressed as plus or minus certain values, should not however be given too much credence since such attempts to evaluate possible errors are dependent to a considerable extent on subjective evaluation of the data. Most of the values for reactivity ratios given are for moderate temperatures, say between about room temperature (20 C.) and 100 C. Of course, the value of the reactivity ratios for a monomer pair is a function of temperature but the variation in reactivity ratios with temperature is quite small and is of little importance unless the polymerization is to be carried out at temperatures considerably removed from those mentioned. Likewise, the reactivity ratios given are for atmospheric or autogenous pressure. Only if the polymerization pressure is to be quite considerably increased will there be an important change in the value of the reactivity ratios. lt may also be pointed out that in the case of highly water-soluble monomers the reactivity ratio values may be shifted somewhat from those given, when polymerization is effected in an aqueous system. Those skilled in the art, having been given the benefit of the present disclosure,`

will be able to evaluate the effect, if any, of reaction conditions on the values given herein and determine the extent of such effect. Similarly, those skilled in the art can determine by Well-known procedures the correct reactivity ratios for monomer pairs not specically set forth in the following tabulation, which tabulation is given by way of example of some but not all of the monomers that are the subject matter of the present invention.

In the following tabulation styrene is considered as M1 and the other monomers in each instance are considered as M2. Substitution of the values for r1 and r2 in the equation given above for the binary polymerization azeotrope composition permits an immediate determination of the proper location for the two points to be placed on the triangular coordinate graph, between which points is drawn the line of clear terpolymers.

For example, if the distance be-` Where M1 is to be vinyltoluene vor vinylxylene, .the same reactivity ratios are used, on the assumption that the` reactivity ratios for suchsystems do not differ essentially for ,the purposes of this invention from the reactivity ratios of the .coir'esponding systems wherein *styrene is M1, This assumes that the introduction ofone or two methyl groups into the aromatic vnucleus-of styrene does not greatly alter the polarity andsteric lproperties ofthe vinyl double bond. Likewise, when analkyl methacrylate other than methyl methacrylateis to be used, the reactivity ratios are assumed not to differ essentially for the purposes of this invention from the above reactivity ratios involving methyl methacrylate. This assumes -that a moderate increase in the chainlength of the alkyl group in the alkyl methacrylates over the single carbon atom in the methyl group of methyl methacrylate, or a branching of the chain if such is present, doesdnot greatly alter the polarity and steric properties of the vinyl double bond. Similar assumptions are made with respect to the vvarious monoalkyl fumarates as a` group and with respect to the various monoalkyl maleates as a group. Anyoneskilled in the art, desiring lgreater precision, can use'well-known standard procedures to determine the reactivity ratios for a given binary system not previously reported in the art. With monomers having fairly long chain alkyl groups, the reactivity ratios tend to diter considerably from' those ifor the corresponding methyl monomer and hence should .be individually determined. Whenever weight percent rather Ithan mole percent is desired as a matter of convenience, mole percentages of the binary azeotrope compositions are easily converted to weight percent by use of the molecular weights of the particular M1 and M2. Injthecase of alkyl methacrylates, monoalkylzfumarates, and monoalkyl maleates, any of whichv can be copolymerized with methyl vinylketone and any one of the monomers styrene, vinyltolene and vvinylxylene in the practice of this invention, special preference is given vto the lower alkyl groups. Alkyl groups containing from l to4 carbon atoms are particularly valuable, viz., methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, sec.butyl, tert-butyl. However, the invention is also applicable to the alkyl compounds mentioned, that contain alkyl groups ofv up to 8 carbon -atoms per alkyl group andev'en4 higher. The following examples illustrate some methods yfor practicing `the present invention with respect to certain ternary mixtures of monomers. The general applicability of the invention, and advantages thereof, are shown in these examples. It will be appreciated that variations can be made in the particular choice of monomers, proportions, and methods of polymerization in accordance with the general teachings of the present specification, and the examples are not to be taken as coextensive with the invention in its broadest aspects.

Example I rThis example, concerns theternary system styrene/ methyl vinyl ketone/acrylic acid. The data obtained in this example are -setforth graphically lin Fig. I of the drawings.

The composition of the styrene/methyl. vinyl ketone binaryaze'otrope vwas calculated in the followingmanner according to the article by Mayo and Walling, Chemical Reviews,46, 199 (1950). 1 f

Styrene 1) 56.1 weight percent styrene, 43.9 weight Metaal erntet-Qa@ (M2) Molecular Weight of methyl vinyl .ketone 70.l Molecular Weight of styrene=l04-l 0.522X 70.1=36.5 grams methyl Vinyl ketone 04784-1041 :49.8 grams styrene 86.3 grams mixture '2 2%):423 Weight percent methyl vill)71 kemne wum weight percet styrene The foregoing calculations give the composition of the styrene/methylvinyl ketone'binary polymerization azeo` trope as 57.7 weight percent styrene, 42.3 weight percent methyl vinyl ketone. `v

By the same procedure, the binary polymerization azeotrope for styrene/acrylic acid was calculated to be percent acrylic acid.

A series of monomeric mixtures was made up, each mixture being prepared by admixture of the individual pure monomers in a Pyrex test tube mm. long and having an internal diameter within the approximate range of 14 to 18 mm., usually about 16 mm. Each test tube containing the particular monomeric mixture was `flushed* with nitrogen in order to remove any air present in the gas' space above the liquid,and the test tube'was then sealedoi at the top by heating the `tube under nitrogen and pulling it out in the ilame to seal the tube completely. Each particular monomer mixture d was prepared and polymerized in duplicate.

A'fter the various tubes containing the monomeric mixtures had been prepared, they were placed in a 90 -C. constant temperature bath, and held there for v24 hours. At the end of that period they were moved` to a l20',C. constant temperature bath and held there for 24 hours. At the end of this second`24-hour period the .tubes were removed and placed in an oven maintained at C. `and ield ytherein for 8 hours. Samples Nos. 3, l0, and 1l were not heated at 180 C. due tothe presence of asmall amount of liquid in the tubes; it was not desired to risk breaking the tubes by the development of excessive. pressurewhichvmight have occurred by virtue of the com paratively-high vapor pressure of the'liquid at theahig temperature. Y

'lhevarious monomeric compositions are set forth in detail in Table I. Table I designates each different mixture by sample number. Sample No. l is approximately the kbinary styrene/methyl vinyl ketone azeotrope com'- position. Sample No. 5 is approximately the binary styrene/acrylic acid azeotrope composition. and 4 have compositions which fall on a straight line connecting the two binary azeotrope compositions, designated Samples NosQl and 5, when plotted on triangular Samples 2, 3,

11 examined visually4 by the same observer, looking through the diameter of the cylindrical body of polymer obtained by breaking and removing the glass tube; this cylinder of polymer conformed to the internal shape and size of the glass tube. These visual observations were checked by other observers.l It was determined that the clarity noted for polymer samples is not significantly affected by variation in polymer cylinder diameter within the range of about 14 to 18 millimeters. It is to be understood that where clarityof polymers is discussed herein, referenceY is made to the appearance on looking through a cylindrical body of the polymer having a diameter within the approximate range of 14 to 18 millimeters. The following words were adopted for describing the clarity of polymers.

C-Clear-essentially crystal clear H-Hazy-some cloudiness but slight T--Turbd-rnoderately cloudy O-Opaque-dense cloudiness-similar to milk glass in appearance Clear" means relatively free from gross amounts of haze but allows the presence of slight haze to be detected with close examination in strong light. Specific notation that a sample was crystal clear means not only that no haze was apparent to the observer, but also that the sample showed a sparkling appearance as found in high'quality crystal glassware.

TABLE 1.-STYRENE/METHYL VINYL KETONE ACRYLIC ACID TERPOLYMERS Referring now to Fig. I of the drawingsfthe clarity data given in Table I have been designated alongside each of the corresponding ternary monomeric mixture compositions indicated by a point on a triangular coordinate` plot. The various numerals on" Fig. I located adjacent the respective points refer to the sample number in Table l. All of the points marked C were rated as clear; of

these, points 3, 4, 7 and 8 had a slight haze but not sutI-' cient to consider them other than essentially clear or to bring them from the clear rating into the hazy rating. Point was somewhat more sparkling than the other samples rated clear. Examination of Fig. I immediately shows that terpolymers prepared from monomeric mixtures having compositions lying on the line joining the two binary azeotrope compositions were clear, as were terpolymers within the area lying along said line.

In Fig. I the dashed lines drawn parallel to the line joining the two binary azeotrope compositions are 5 percent on each side of the line, i. e., each is a distance from the line equal to 5 percentage points of composition as determined by dividing the distance between an apex and the center of the opposite side of the triangle into 100` equal equidistant parts. All terpolymers prepared from monomeric mixtures having compositions falling withinithe area within 5 percent of each side of the line are clear. Some `of those taken from areas appreciably beyond the 5 percent value are clear; see for exshaman ample point 8, which is clear. However, point 9 lying somewhat farther from -the line than point 8 is not clear but turbid. It is also seen that points l0, 11 and l2 on the opposite side of the lineare beyond the area of clear terpolymers.

' Example 2 This example presents data on the ternary system `vinyltoluene/methyl vinyl lretone/methacrylonitrile.`

The reactivity ratios forthe system vinyltoluene/ methyl vinyl ketone and for the system vinyltoluene/methacrylonitrile were assumed not to differ essentially for the purposes of this invention from the reactivity ratios of the corresponding systems styrene/methyl vinyl ketone and styrene/methacrylonitrile, respectively. This as sumes that the introduction of a methyl group into the aromatic nucleus of styrene does not greatly alter the polarity and steric properties of the vinyl double bond. Mole ratios for the two binary polymerization azeotropes were calculated in the manner described in the preceding example, and these were then converted to weight ratios, employingthe molecular weight of vinyltoluene in each instance instead of the molecular weight of styrene.

In this manner the binary polymerization azeotrope composition of vinyltoluene/methyl vinyl ketone was calculated to be 60.8 weight percent vinyltoluene, 39.2 percent methyl vinyl ketone. Similarly, the binary polymerization azeotrope composition of vinyltoluene/methacrylonitrile was calculated to be 67.9 weight percent vinyltoluene, 32.1 weight percent methacrylonitrile.

Samples were prepared and tested in the manner set forth in Example 1. The vinyltoluene employed in these tests was a mixture of isomeric metaand para-methylstyrenes.

Samples l to 5, inclusive, fall on the line joining the two binary polymerization azeotrope compositions. Samples 6 and 7 were selected to lie fairly close to the line and on opposite sides of the line. the greatest distance from the line in the direction of increasing vinyltoluene content, whereas Samples 10, 1l and 12 are on the opposite side of the line and cover a variety of compositions. The data on compositions and polymer products are set forth in Table ll, and shown graphically in Fig. II of the drawings.

TABLE IL VINYLTOLUENE/METHYL VINYL KETONE/ METHACRYLONITRILE TERPOLYMEHS Compo- Appearance sitlon, Sample weight N o. percent VT/ Clarity Color MVK] MN 61/39/ 0 Colorless. 62/33/ 5 Very light yellow.

Light yellow.

Do. Colorless. Light yellow.

Do. White.

Do. Yellow. Orange. Do.

VTzvinyltoluene. MVK-Methyl vinyl ketone.

MN==Methacrylonltrile.

It will be noted in examining the drawing and data that all of the polymers made from monomeric mixtures whose compositions lie on the line joining the two binary polymerization azeotropes were clear, as were those made from mixtures having compositions fairly close to the line (points 6 and 7). In contrast, those polymers made from ternary mixtures having compositions on either side ot the line but at a considerable distance from the line,. i. e., points 812, were not clear but rather range from very. hazy'` through turbid and opaque. It is interesting to note that points 10, 11 and 12 below the line are 30 percent Samples 8 and 9,lie

and more away from the lineand yet only hazy or turbid, whereas points 8 and 9. abovethe line are -icloser *to the line (15 to 20 percent away) and yet are opaque. Such behavior is consistent with most physical phenomena which seldom exhibit perfect regularity.

Another interesting thing tor note .is that by the practice of the present invention as applied to these monomers, terpolymers of minimum color result. Thus, the sampleson and near the line are at the most light yellow in` color, Whereas. those farther' away from the 4line are yellow, orange or opaque white.`

.As in Fig. I, dashedlines have been drawn in Fig. II which are percent away from lthe 'line on eachy side ofthe line, and terpolymers prepared from monomeric mixtures Whose compositions lie within `thesefS percent lines are preferred products ofthe invention. However, the invention yin`its broadest aspects encompass terpolymers prepared from monomeric mixtures having compositionswithin the entire area of clear terpolymers Example 3 20 This `example presents data I on the ,ternary :systemstyrene/methyl vinyl ketone/methyl methacrylate.

In the manner set forth in Example '1, the binary polymerization azeotrope composition of styrene/methyl vinyl ketone was calculated tov be 57.7fweight percent styrene, 42.3 weight percentmethyl vinyl ketone.. Similarly, the bin-ary polymerization azeotrope composition for :styrene/methyl methacrylate was calculated `to :be 53.9 weight percent styrene, 46.1 Aweight percenvtlmethylmethacrylate. y

Samples containing varying proportions'of the monomers were prepared and polymerized :and observations made .on thev polymers inthe manner described in Examplel I. These data are listed in Table III and plotted in Fig. III of the drawings. It'will be `seen that points ilfto .'6, inclusive, were on or approximately on the line joining the two binaryv azeotrope compositions, :that points 7 and.8 `werea few percentage points away from :the line on opposite sides of the line, that points 9 and 10` were a farther distance from the line in the direction of kin-V creasing styrene content, while points :1l-16, inclusive were on. the opposite side ofthe linefand coveredawide TABLE IIL-STYRENE/METHYL VINYL KETONE/MATHYL METHACRYLATE' TERPOLYMERS Compo- Appearance sltion, Sample Wt. per- 55 `No. cent S/MVK/ Clarity Color 1 54/ 0/46 C-Clear (crystal clear) Colorless. 2 54/ 8/88 .do y.-. Do.

i C-Clear (v., v. sl. haze)- Do. 60 C-Clear 2v. sLhuze) Do. C-Clear sl. haze) Do. -.do Sl. yellow. C-Clear (crystal clear).- Colorless. C-Clear (sl. haze) Do.

' WhltDe. i

O. r Colorless. 60

De. 30/55/15 Light yellow. l /60/20 White tolight yellow. 10/45/45 H-Hazy (very).-. Do. /70/ 5 O-Opaque White. 70

.S Styrene.

MVK= Methyl vinyl ketone.

' MMA= Methyl methacrylate.

v. Very. sl.=Slight.

the clarity of terpolymers prepared from monomeric mixtures. lwhose composition. is taken from vthe line joining the two vbinary polymerization azeotrope compositions andgthearea lying ralong the line. gAs notedin other instances, clarity disappearsrrnore quickly above the lineias higher concentrations of styrene are approached than .it

does `below the line. Thus, vthe area ofvclear terpolymers l below the line, i; e., in the direction ofr decreasing styrene concentration, is quite large, points 11, 12 and A13 ,being clear. However, in this direction also the area of clarity is limited, as shown by the kfact that points 14, l5` and'l6 are opaque, very hazy and opaque, respectively. As in the `other gures, a dashed linefhas been drawn on each side of the line joining the two'binary azeotrope compositions, at a distance of 5 `percent from the line, setting.

forth a preferred area of monomer compositions for ,uSe in making terpolymers with lthese monomers'.

While the linvention has vbeen described herein ywith particular reference to various preferred embodiments thereof, and examples havegbeengiven `ofsuitable proportions vand conditions, it will be appreciated that variations styrene,ivinyltoluene, and vinylxylene.- (b) methylyinyl ketone, and (c) a monomer selectedfromrthe group ,consisting of acrylic` acid, ymethacrylic acid, -methaerylonitrile',k alkyl methacrylate, monoalkyl fumarate, Vmonoalkyly maleate, theproportions of the three monomers in 'saidy monomeric mixture being limited to those in the area of mixtures that produce' clear terpolymers saic1,area en` compassingthe line joining-the polymerization azeotrope composition of the particular (a) and methyl vinyl ketone on the one hand and the particular (la) and the parv yticular (c) on the other hand as plotted on an equilateral triangularv coordinate graph. v

A2. YA clear-terpolymer prepared by free-radical-initiated batch masspolymerization of a monomeric mixturecon sisting of ,(a) a monomer selected from the groupconsisting of styrene, vinyltoluene, and vinylxylene, (lb.)

ymethyl vinyl ketone, and (c) a monomergselected-from (a) and the particular (c) on the other hand as plotted l on an equilateraltriangular coordinate graph.

3. A clear terpolymer prepared byjfree-radical-initiated batchpolymerization of a monomeric mixture. consisting of (a) styrene, (b) methyl vinyl ketone, (c) -amonomer selected'from. the group consisting of acrylic acid, methacrylic acid, methacrylonitrile, alkyl methacrylate, monoalkyl fumarate, monoalkyl maleate, the proportions of the three monomers in said monomeric mixture being limited to those in the area of mixtures that produce clear terpolymers, said area encompassing the line joining 4the polymerization lazeotrope composition of styrene and methyl vinyl ketone on the one hand and styrene and the particular (c) on the other hand as plotted on an equilateral triangular coordinate graph.

4. A clear terpolymer prepared by free-radical-initiated batch polymerization of a monomericmixture consisting of (a) vinyltoluene, (b) methyl vinyl ketone, and (c) amonomer selected from the group consisting of r acrylic 15 acid, methacrylic acid, methacrylonitrile, alkylfmethacrylate,` monoalkyl furnarate, monoalkyl maleate, the pro portions of the three monomers in said monomeric mixture being limited to those in the area of mixtures that produce clear terpolymers, said area encompassing `the line joining the polymerization azeotrope composition `of vinyltoluene and methyl` vinyl ketone on the one hand and vinyltoluene and the particular (c) on the other hand as plotted on an equilateral triangular coordinate graph.

5. A clear `terpolymer prepared by free-radical-initiated batch mass polymerization of a monomeric mixture con sisting of (a) styrene, (b) methyl vinyl ketone, and (c) a monomer selected frornthe group consisting of acrylic acid,` methacrylic acid, methacrylonitrile, alkyl methacrylate, monoalkyl fumarate, monoalkyl maleate, the proportions of the three monomers in said monomeric mixture beingflimited to those in the area of mixtures that produce clear terpolymers,' said area encompassing the line joining the polymerization azeotrope composition of styrene and methyl vinyl ketone on the one hand and styrene and the particular (c) on the other hand as plotted onv an equilateral triangular coordinate graph.

6. Aclear terpolymer prepared by free-radical-initiated batch mass polymerization of a monomericmixture consisting of\(a) vinyltoluene, (b') methyl vinyl ketone, and (c) a monomer selected from the group" consisting of acrylic acid, methacrylic acid, methacrylonitn'le, alkyl methacrylate, monoalkyl fumarate, monoalkyl maleate, the proportions 'of the three monomers in said monomeric mixture ibeing limited to those in the area of mixtures that produce clear terpolymers, said area encompassing the `line -joining the polymerization azeotrope compositiony of `vinyltoluene'and methyl vinyl ketone on the `one hand and vinyltoluene and the particular (c) on the other hand as plotted ony an'equilateral triangular coordinate graph r 7. A clear terpolymer prepared by free-radical-initiated batch polymerization to a conversion of at least 20 `weight percenty of a monomeric mixture consisting of `(a) a monomer selected from the group consisting of styrene, vinyltoluene, and vinylxylene, (b) methylvinyl ketone, and (c) a monomer selected from the group consisting of acrylic acid, methacrylic acid, methacrylonitrile, alkyl methacrylate, monoalkyl fumarate,` monoalkyl maleate, tht-.proportions of the three monomers in said monomeric mixture beinglimited to those in the area of mixtures that. produce clear terpolymers, said area encompassing the line joining the polymerization azeotrope composition of the particular(a) and methyl vinyl ketone on the one hand and the particular (a) and the particular (c) on the other hand as plotted on an equilateral triangular coordinate graph.`

8;l A terpolymer `according to claim 1 wherein (c) -is acrylic acid. 4 t

9.v A terpolymer according to claim 1 wherein (c) is methacrylonitrile. t Y

10. A terpolymer according to claim l wherein (c) is an alkyl methacrylate.

l1; A terpolymer according to claim l wherein (c) is methyl methacrylate. n

12.` A clear terpolymer prepared by free-radical-initiated` batch polymerization of a monomeric mixture consist ing of (a) styrene, (b) methyl vinyl ketone, and(c) acrylic acid, the proportions of the three monomers inl area of 'mixtures that produce clear terpolymers, said area encompassing the line joining the polymerization azeotrope composition of vinyltoluene and methyl vinyl ketone onthe one hand and vinyltoluene and methacrylonitrile on the other hand as plotted on an equilateral triangular coordinate graph.

14. A clear terpolymer prepared by free-radical-initiated batch polymerization of` a monomeric mixture consisting of (a) styrene, (b) methyl vinyl ketone, and (c) methyl methacrylate, the proportions of the three monomers in.

said monomeric mixture being limited to those in the area of mixtures that produce clear terpolymers, said area encompassing the line joining the polymerization azeotrope composition of styrene and methyl vinyl ketone on the 4one hand and styrene and methyl methacrylate on the other hand as plotted on an equilateral triangular co ordinate graph.

1S. A polymerization process whichy comprises forming a three-component monomeric mixture consisting of (a) a monomer selected from the group consisting of styrene, vinyltoluene, and vinylxylene, (b) methyl vinyl ketone, and (c) a monomer selected from the group consisting of acrylic acid, methacrylic acid, methacrylonitrile, alkyl methacrylate, monoalkyl fumarate, `monoalkyl maleate, the proportions of the three monomers in said monomeric mixture being limited to those in the area of mixtures that produce clear terpolymers, said area encompassing the line joining the polymerizationazeotrope composition of the particular (a) and methyl vinyl ketone on the one hand and the particular (a) and the par ticular (c) on the other hand as plotted on an equilateral triangular coordinate graph, and subjecting a batch of said monomeric mixture to free-radical-initiated batch polymerization forming an essentially clear homogeneous high molecular weight terpolymer.

16."A polymerization process `which comprises forming athree-component monomeric mixture consisting of (a) styrene, (b) methyl vinyl ketone, and (c) a monomer selected from the group consisting of acrylic acid, methmethacrylonitrile, the proportions of the three monomers in said monomeric mixture being limited to those in the of said monomeric mixture to free-radical-initiated batch mass high conversion polymerization forming an essentially clear homogeneous high molecular weight terpolymer.

17. A process according to claim 15 wherein said monomeric mixture consists of (a) styrene, (b) methyl vinyl ketone, and (c) acrylic acid.

18. A process according to claim 15 wherein said monomeric mixture consists of (a) vinyltoluene, (b) methyl vinyl ketone, and (c) methacrylonitrile.

19. A process according to claim 15 wherein said monomeric'mixture consists of (a) styrene, (b) methyl vinyl ketone, and (c) methyl methacrylate.

20. A clear terpolymer prepared by free-radical-initiated batch polymerization of a monomeric mixture consisting of (a) a monomer selected from the group consisting of styrene, vinyltoluene, and vinylxylene, (b) methyl vinyl ketone, and (c) a monomer selected from the group consisting of acrylic acid, methacrylic acid, methacrylonitn'le, alkyl methacrylate, monoalkyl fumaratc, monoalkyl maleate, the proportions of the three monomers in said monomeric mixture being limited to those in the area of mixtures that produce clear terpolymers, said terpolymers, said area encompassing the line joining the polymerization azeotrope composition of the particular (a) and methyl vinylketone on the one hand and the particular (a) and the particular (c) on the other hand as plotted 17 on an equilateral triangular coordinate graph, but not more than 5 percent away from said line.

21. A clear terpolymer prepared by free-radical-initiated batch polymerization of a monomeric mixture consisting of (a) a monomer selected from the group consisting of styrene, vinyltoluene, and vinylxylene, (b) methyl vinyl ketone, and (c) a monomer selected from the group consisting of acrylic acid, methacrylic acid, methacrylonitrile, alkyl methacrylate, monoalkyl fumarate, monoalkyl maleate, the proportions of the three monomers in said monomeric mixture being designated by the line joining the polymerization azeotrope composition of the particular (a) and methyl vinyl ketone on the one hand and the particular (a) and the particular (c) on the other hand as plotted on an equilateral triangular coordinate graph.

22. A clear terpolymer prepared by free-radical-initiated batch polymerization of a monomeric mixture consisting of (a) styrene, (b) methyl yinyl ketone, and (c) an alkyl methacrylate, the proportion of the three monomers in said monomeric mixture being limited to those in the area of mixtures that produce cleal terpolymers, said area encompassing the line joining the polymerization azeotrope composition of styrene and methyl vinyl ketone on the 18 one hand and styrene and said alkyl methacrylate on the other hand as plotted on an equilateral triangular coordinate graph, but not more than 5 percent away from said line.

23. A clear terpolymer prepared by free-radical-initiated batch mass polymerization of a monomeric mixture consisting of (a) styrene, (b) methyl vinyl ketone, and (c) methyl methacrylate, the proportions of the three monomers in said monomeric mixture being designated by the line joining the polymerization azeotrope composition of styrene and methyl vinyl ketone on the one hand and styrene and methyl methacrylate on the other hand as plotted on an equilateral triangular coordinate graph.

References Cited in the tile of this patent UNITED STATES PATENTS DAleiio oct. 2o, 1953 OTHER REFERENCES Alfrey et al.: Copolymerizatiom Interscience, 1952, pp. 123, 124, 128 and 129.

UNITED STATES PATENT OFFICE Certificate of Correction Patent N o. 2,829,125 April 1, 1958 Robert J. Slocombe et al.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the .said Letters Patent should read as corrected below.

line.)-; line 52, after along insert -and encompassingcolumn 5, line 47, after area strike out being, rst occurrence; column 9, line 46, for vinyltolene read -vinyltoluene-; column l0, line 16, for 04784-1041 read -0.478 104.1; column 11, line 71, after parts and before the period insert in other words, the two dashed lines are on opposite sides of and 5 graphical units distant from said line-; column 16, line 71, after the first comma strike out said terpolymers,; column 17, lines 1 and 2, strike out but not more than 5 per cent away from said line. and instead -with the further limitation that said proportions of the three monomers are restricted to the area of said graph bounded by two lines on opposite sides of and parallel to and 5 graphical units distant from said line.-; column 18, lines 3 and 4, strike out but not more than 5 per cent away from said line. and insert instead `with the further limitation that said proportions of the three monomers are resricted to the area of said graph bounded by two lines on opposite sides of and parallel to and 5 graphical units distant from said line.-. Y

Signed and sealed this 4th day of November 1958.

atteso KARL H. AXLINE, ROBERT c. WATSON, Attestz'ng Ojcer. @ammissioner of Patents. 

1. A CLEAR TERPOLYMER PREPARED BY FREE-RADICAL-INITIATED BATCH POLYMERIZATION OF A MONOMERIC MIXTURE CONSISTING OF (A) A MOMOMER SELECTED FROM THE GROUP CONSISTING OF STYRENE, VINYLTOLUENE, AND VINYLXYLENE, (B) METHYL VINLY SISTING OF ACRYLIC ACID, METHACRYLIC ACID, METHACRYLONITRILE, SISTING OF ACRYLIC ACID, METHACRYLIC ACID, METHACRYLONITRILE, ALKYL METHACRYLATE, MONALKYL FUMARATE, MONALKYL MALEATE, THE PROPORTIONS OF THE THREE MONOMERS IN SAID MONOMERIC MIXTURE BEING LIMITED TO THOSE IN THE AREA OF MIXTUES THAT PRODUCE CLEAR TERPOLYMERS, SAID AREA ENCOMPASSING THE LINE JOINING THE POLYMERIZATION AZEOTROPE COMPOSITION OF THE PARTICULAR (A) AND METHYL VINYL KETONE ON THE ONE HAND AND THE PARTICULAR (A) AND THE PARTICULAR (C) ON THE OTHER HAND AS PLOTTED ON AN EQUILATERAL TRIANGULAR COORDINATE GRAPH. 